Kinetograph movement driving mechanism



Dec. 2l, 1965 Filed Aug. 5, 1965 G. A. MITCHELL KINETOGRAPH MOVEMENTDRIVING MECHANISM @Jin 4 Sheets-Sheet 1 MTM@- Dec. 21, 1965 G. A.MITCHELL 3,224,656

KINETOGRAPH MOVEMENT DRIVING MECHANISM Filed Aug. 5, 1963 4 Sheets-Sheet2 .5w/Evra?. EaPE-A. Azra/5.1.5

Dec. 21, 1965 G, A, M|TCHE| 3,224,656

KINETOGRAPH MOVEMENT DRIVING MECHANISM Filed Aug. 5, 1963 4 Sheets-Sheet5 @Eaeas A. Mrs/wsu.,

Dec. 21, 1965 G, A. MITCHELL KINETOGRAPH MOVEMENT DRIVING MECHANISM 4Sheets-Sheet 4 Filed Aug. 5, 1963 650255./1. Jil/mwa, TWs/woe o@ BHdl/ance nyu/an United States Patent O 3,224,656 KINETOGRAPH MOVEMENTDRIVING MECHANISM George A. Mitchell, 687 Prospect Crescent, Pasadena,Calif.

Filed Aug. 5, 1963, Ser. No. 299,796 17 Claims. (Cl. 226 57) Thispresent application is a continuation in part of my previous applicationSerial No. 267,478, filed March 25, 1963 now abandoned, for RegisterActuation for Kinetograph Movement.

This invention has to do with a novel cam mechanism for drivingelements, such as registration members and claw arms, of movements forkinetograph mechanisms. That prior application described one form of mycam mechanism driving an improved form of pilot pin device. The presentapplication adds to that disclosure another form of the novel cammechanism, the driving of the pilot pin device by that other form, andthe driving of a film moving claw arm by both forms of the cammechanism.

In the improved driving cam mechanism the cam element or unit, drivesthe driven element, such as pilot pin or claw arm with relatively longstationary dwells and very fast movement strokes, and with the drivenelement constantly held against loose movement between two opposedfollowers. The fast movement strokes, which involve slow rather thansudden acceleration and deceleration, are due to cooperatingconfigurations of the cam element and the follower elements, as will bedeveloped below. As an example, with the present cam mechanism the filmmoving stroke of a claw arm may typically occupy as little as 22 ofdriving shift and shutter rotation, leaving as much as 320 for totalshutter opening with an allowance of 18 for shutter safety.

The characteristics of the invention will best be understood from thefollowing descriptions of typical forms of cam elements drivingcooperating follower elements which drive such driven elements as pilotpin and claw arm. Reference is had to the typical and illustrativeembodiments shown in the accompanying drawings, in which:

FIG. 1 is an elevation showing the application of the presentimprovement to a film registration element also of improved design;

FIG. 2 is an end elevation of the same;

FIGS. 3 and 3a are sections on line 3 3 of FIG. 2, showing the registerelement, respectively in and out of film engagement;

FIG. 4 is a section on line 4 4 of FIG. 3;

FIG. 5 s a schematic view similar to FIG. 3 showing a modified cammechanism;

FIG. 6 is a section on line 6 6 of FIG. 5;

FIG. 7 is a general elevation showing `a claw arm movement in itsposition of upper dwell shortly before the start of its film-moving downstroke, driven by the type of cam mechanism shown in FIGS. 3, 3a;

FIG. 8 is a section on line 8 8 of FIG. 7;

FIG. 9 is a section on line 9 9 of FIG. 7;

FIG. 10 is a schematic showing the movement at the start of thedown-stroke;

FIG. 1l is a similar schematic showing the movement at the finish of thedown-stroke;

FIG. l2 is a similar schematic showing the claw withdrawal at the end ofthe dwell at the bottom of the downstroke;

FIG. 13 is a similar schematic showing the end of the up stroke, theupper dwell being between the positions of FIG. 13 and FIG. 10;

FIG. 14 is a side elevation similar to FIG. 7, showing the claw armdriven by the modified cam mechanism of FIG. 5 at reduced scale;

FIGS. l5 and 16 are sections on lines 15 15 and 16 16 of FIG. 14;

FIG. 17 is a diagram illustrating the relative movements of a cam memberand follower; and

FIG. 18 is a diagram showing the resultant movement pattern of thefollower plotted against cam rotation.

FIGS. l to 6 show the improved cam mechanism driving a film registryelement in the form of a pilot pin. Reference is first made to FIGS. 1to 4.

In those figures a movement driving shaft is indicated at 20, driving aclaw arm 22 by cam operation to advance its claw or claws 24 into filmperforations, then move the film F down through race 26 and thenwithdraw from the film and move back upwardly for the next cyclebeginning with advance for film engagement, The nature of the improvedcam drive and the claw path of the claw arm are not shown here, but inFIGS. 7 and following. The register means is here shown as embodying theusual register pin or pins 28 adapted to move in and out of filmperforations, to register the film during its dwells and successivemovements of the claw arm. As here shown, the register pin 28 ridesflatly on a guide 30 mounted on a fixed part 32 of the film race. Thepin or pins 28 are carried on the forward end of a reciprocating shaft34 which is reciprocatingly operated by cams on driving shaft 20. Shaft34 reciprocates in slide bearings formed in lugs 36 on fixed plate 38.

In the form of FIGS. 1 to 4 driving shaft 20 carries two registeroperating cams 40 and 42 which, respectively, operate on cam followerarms 44 and 46 that depend from members 48 and S0 that are generallycylindric in form and lit closely slidingly on shaft 34. The two members48 and 50 are held in mutual endwise abutment by a spring 52 seated onsnap ring 54 on shaft 34, pressing 48 against 50. Member S0 is seatedagainst a cam member 56 which in turn is seated against snap ring 58 onshaft 34. A cam formation 60 on 50 and 56 causes relative withdrawingmovement (to the right in the drawings) of shaft 34 when member 56 isswung by handle 62 about shaft 34 through a suitable angle, say of 90.As explained later, the two cam follower arms 44 and 46 and theirmembers 48 and 50 are held by cam engagement in a fixed position (forany angular position of the cam shaft 20) so that pilot pin 28 will bewithdrawn from film engagement by swinging the camming member 56 t0withdraw shaft 34 relative to the members 48 and 50. It may be remarkedhere that the two cams 40 and 42 form, in effect, a composite cambetween the two follower arms 44 and 46. Those two arms may then beaccurately fitted for close bearings on the cams by grinding and/orlapping the abutting surfaces 66 of members 48 and 50. As will be notedfrom the drawings, members 48 and 50 with their follower arms 44 and 46are duplicates of each other except that, as shown, 50 has the camformation at 60. However, member 48 may also, without harm, carry thesame cam formation on its end engaged by spring 52; so that both membersmay be exact duplicates.

As shown in FIGS. 2 and 4, cams 40 and 42 are axially offset on shaft20. Disks 70 lie at opposite sides of the two cams and confine followerarms 44 and 46 which are offset on members 48 and 50 corresponding tothe Icam offsets. Disks 70 keep the followers 44 and 46 in camengagement, preventing them and their members 48 and 50 from swingingabout register shaft 34.

As will be understood from the description thus far,l

the distance between the follower faces 44a and 46a of the followers 44and 46, measured in a directional normal to the axis of shaft 20 andparallel to shaft 34, is a fixed quantity. More accurately speaking, thesum of the radial distances from that shaft axis to the planes of 44aand 46a is a fixed measure. Cam 40 operates on follower arm 44; cam 42on follower arm 46. And the shapes of those two cams and their followerfaces are such that both cams are always in follower engagement, orleast, always in such engagement during the critical periods of registeroperation.

FIGS. 3 and 3a show the positions of cams 40 and 42 in the middles oftheir positions for, respectively, pilot pin fully projected Iand fullywithdrawn. Cam 40, operating on follower 44, is circular about the axisof shaft 20 from such a radial line as indicated at 80 to such a radialline as indicated at 80a. Assuming cam rotation in the directionindicated, follower 44 will be positively held to the left, with thepilot pin projected, during that cam rotatioin from 80 to 80a, throughan angle, as here shown, of approximately 235. Consonantly, cam 42,engaging follower 46 is circular about the shaft axis between the tworadial lines indicated at 82 and 82a. The angular distances between 80,80a and 82, 82a, are equal. The radius of the circular arc of cam 42 isless than that of the circular arc of cam 40 by an amount equal to thetotal cam actuated movement of the pilot shaft 34; and those two arcsare diametrically opposed about the axis of shaft 20. Consequently,pilot pin 28 is positively held immovably in its projectedfilm-registering position during rotation of the cams through the anglesmentioned.

FIG. 3a shows the cams rotated from the position of FIG. 3; in theirmedial position for retracting the pilot pin. In this position, acircular arc of cam 42, lying between such radial lines as indicated at84 and 84a, engages follower 46 to hold the pilot retracted. As hereshown, the angle of that arc is about 50. As here shown, the radius ofthat arc about the axis of shaft 20 is the same as the radius of thecircular arc of cam 4t) between 80 and 80a. In this position of thecams, a diametrically opposed circular arc of cam 40, lying between thelines indicated at S6 and 86a, and also of about 50, and of radius hereshown as equal to the smaller radius of the circular arc of cam 42 thatlies between the lines 82 and 82a, is in engagement with follower 44.Consequently during the angular cam rotation through the 50 angles 84 to84a and 86 to 86a, the pilot is positively held immovably in theretracted position.

On cam 40 the runs between the smaller radius arc 86-86a and the largerradius arc Sil-80a, in the aspects of FIGS. 3, 3a, are here shown asstraight lines tangential to the arc S45-86a of smaller radius.Likewise, on cam 42, the runs between the smaller radius arc 82-82a andthe larger radius arc S4-84a are shown as straight lines tangential toarc 82-82a. The straight line runs, `as :shown in FIGS. 3-3a of the twocams are diametrically opposed. Throughout the diametrically opposedrotational angles of the circular arcs on the two cams, the cam elementor unit is of course of constant diameter. But the cam diameters throughthe shaft axis between points on the straight line runs, such asdesignated 87 and 87a in FIG. 3a, is not itself constant and, as pointedout later, it is the opposing convex shapes of the follower faces 44aand 46a that keep the cam unit always snugly engaged between thefollower faces during those straight line runs of the cam unit, as wellas during the cam rotation through the angles of their opposed circulararcs. In full effect the follower shape makes the cam mechanism to actas a constant diameter cam, as well as to give the followers slowacceleration and deceleration as hereinafter developed.

The, shapes of the two cams through the rotational angles between thecircular arcs, and the shapes of the followers, are so related that,during the shifts of the pilot between protracted and withdrawnpositions, each cam is constantly in engagement with its respectivefollower; so that, at no cam position is the pilot and follower ensembleallowed to be shiftably loose and subject to chattering, etc.

" of movement shaft 20 and the associated shutter.

The several rotational angles of the cam formations are, of course,designed to shift the pilot in synchronism with the operation of thefilm movement. That movement is lhere shown as a claw, but may be of anytyp-e. As applied to a claw movement the cam angles are preferablydesigned to project the pilot pin into a film perforation as the clawpulls out of its engaged perforation and to withdraw from the pilotperforation as the claw moves into its next perforation preparatory tomoving the film. The film is thus normally continuously engaged by theclaw and pilot; the cam at 60 withdrawing the pilot to free the film forthreading, etc.

Although the respective major and minor radii of the two cams are hereshown as equal, that is not at all necessary to the described operationof the pilot nor to that of the claw arm later described. It is onlynecessary that the respective differences, in the two cams, betweentheir major and minor radii be equal. This is also true of the same typeof composite cam device driving the claw arm as in FIGS. 7 andfollowing.

There are several distinct advantages inherent in the described pilotactuation by a cam unit of two cams. One is fast pilot shifting, whichresults in a longer period of film dwell, here approximately 235 ofrotaton nu other lies in the positive immovable holding of the pilot inits projected film engaging position. That eliminates all sawing of thefilm perforations during that period of pilot projection and theaccompanying film displacement due to such sawing. And the fact that thepilot is held immovably during projection, makes it possible to useregistration means other than a perforation entering pilot pin. Forexample, a film clamping pressure foot might, on projection, clamp thefilm against an opposite surface of the film race. Such clamping howeverhas no function in registering the film position. The standardly usedclaw type movement has a claw or claws smaller in crosssection than thefilm perforations, to take care of film shrinkage. Thus, such a clawmovement does not leave the film in registered position. Register pins,on the other hand, are of cross-sectional size in either one or bothdimensions equal to the corresponding perforation dimensions. With aslight forward end taper they thus move and hold the film in registeredposition, and for that reason are here preferred.

Each of the cam follower arms 44 Vand -46 has, instead lof a fiat innercam contacting face, a convexly curved `face such as shown at 44a and46a. As here shown these convex lobe formations have a curvature radiusapproximately the same as the largest radius on the cam-s. Theparticular results of such convex cam contacting lobes are mainly due tothe fact that the line or point of ca-m contact during cam rotationthrough -the angles of changing radius-as for instance in the angle .ofapproximately 35 between 80 and 86 on cam 4tlthat line of contact movesvertically on the contact faces 44a and 46a of 44, 46 hy Ia much smalleramount than such movement on a flat Contact face. Result is that duringall angles of cam Irotation the cams much more accurately'fill, so tospeak, the spacing between the follower conta-ct faces, with significantreduction of chatter noise due to looseness. And the cam producedrreciprocation of the register shaft and pins follows a sine curve withgradually increasing and decreasing velocities, without any sud-denaccelerations and decelerations. The reasons for .this are mo-re fullydiscussed `after the later descriptions of such Aa driving cam mechanismapplied to a claw arm.

FIGS. 5 land 6 show how the two followers 44 and 46 may -be driven by asingle cam 90. This cam has an arc 92 of the larger radius and Iof angleabout 162 lying between the radial lines indicated at 94, 96. Adiametrically opposite arc 93 of the smaller radius .also extendsthrough .the same angle between the lines 94, 96. Between the ends ofarcs 92 and 93, the cam has, as in the form of FIGS. 3, 3a, a peripheryof changing radius along lines 98 which are formed `by straight camfaces tan-gent t-o the arc 93 of smaller radius. In FIGS. 3, 3a, thecorresponding peripheries Iof chang-ing radii lie between the radiallines 80-86, Stia-86a, 82-84a, yand 84-82a. In FIGS. 5 and 6, the camrotative angle of pilot pin shift is appro-ximately 18, between theradial lines 94-96. Here again the shift is fast and the curvatures offollower faces 44a and 46a cooperate with the cam configuration t-o giveslow accelerations and decelerations and constant snug engagement of thecam between t-he followers. It has been found that the optimum in thatregard is with the radius of curvature of 44a yand 46a (in either thesefigures or in FIGS. 3, 3a) approximately equal to, but slightly greaterthan, the larger of the two cam radii; and the radii of 44a and 46a arehere so shown. As will be further developed, a .radius for 44a, 46a muchlarger or materially smaller than the larger cam radius leads tolooseness between the cam or cam assembly during transition and torela-tive suddenness of acceleration and decelerati-on of the cam drivenelement.

FIGS. 7 to 13 show the application of the improved forms of cam`mechanism to `an improved form of film moving claw arm. In thesefigures the scale is approximately twice the dimensions of a design for16 mm. fi-lm and the dimensions later noted in illustration are for sucha design.

The physical form of the claw movement is shown in FIGS. 7, 8 and 9. Asthere shown, the claw arm consists of a plate member 120, carrying claw122 at one end and having a sliding pivotal mounting at the other end.As sh-own here that sliding pivotal mounting consists of a fixed pivotpin 124 and sliding pivot Ways 126 on the claw arm, although thelarrangement might be reversed with pin 124 mounted on the arm andpivotally sliding in ya fixed way.

Plate member 120 lies between the two complementary cams 130 and 132fixedly mounted for rotation on and by driving shaft 134. In its portionbetween the two cams and around :shaft 134 plate member 120 has arectangular opening 136 accommodating a cam 138, shown a-s aconventional constant diameter heart-shaped cam, which acts, as will bedescribed, to shift the claw arm for claw project-ion and retraction.The three cams may be fixed lon shaft 134, axially and t-o rotatetogether with the shaft, in any suitable manne-r.

Plat-e me-mber 120 also carries at its upper portion a cam follower 140offset into the plane of cam 130 4as shown in FIG. 8. Also that mainplate carries another cam follower 142 at its lower portion, offsetoppositely to Ifollower 140 and into the plane of cam 132, as shown inthat ti-gure. Each of these followers has an inner curved, preferablycircular cam contacting inner edge face 144, 146, typically of radiiabout equal to the larger radius of the two cams 130 and |132. As shownhere the center of circular follow-er face 144 is located at 145 andthat of circular follower face 146 is at 147. As here shown the centers145 and 147 are located diametrically opposite each other about the axisof shaft 134 (except for the small amount of in and out shift) and theradii of follower faces v144 and 146 about equal to, and preferablyslightly larger than the larger cam radius.

yIt will be noted that cams 130, 132 and 138 as well as the claw arm120, fare plateelike members. The cams may, for instance, be form-ed bystamping or similar operations. Claw arm member 120 may likewise beformed, with its `cam followers 140 and 142 by stamping and embossingoperations. All four of these members may be initially formed of somerelatively soft metal, as, for eX- ample, of a soft aluminum alloy suchas that known as 2024. Such an alloy may then, after formation of theparts and initial heat treatment, be surface hardened by using such aprocess as that known as Kanigen, followed by another yand lowertemperature heat treatment; so that in their finis-hed forms all therelatively moving parts `of the claw movement are hard surface finishedand long Wearing.

As shown in FIG. 7, cam has an arc periphery 150, here designed as of 60extent, between the two radial lines a and b, and of what is |herecalled the smaller radius. Leading tangentially from the ends of thatare of 60 extent, cam 130 has two substantially straight shift faces 151and 152, leading to t-he ends of an arc face 154 at what is here calledthe larger cam radius. That larger radius arc extends laround cam 130,in :the design as here shown, for about 230 :between the radial linesdesignated e and f.

Complementary to cam 130, calm 132 has an arc periphery 160, at thelarger radius, between the radial lines c and d which lieidialmetrically opposite the radial lines a and b `of cam 130. From eachend of that 60 arc of larger radius cam 132 has shift faces `161 and 162leading tangentially into the are of cam face y164 which also extendsaround cam 132 for about 230. It will be noted that the arc faces i and160 `on the two cams `are diametrically opposed, Vas are also the twoarc faces 154 and 164. The shift faces 151, 161 and 152, 162 larelikewise diametrically opposed and of equal angular extent of about 35each.

In an actual illustrative design, here shown at approximately twicescale, the larger cam radius is about 12.2 mm., the smaller, about 10mm.; and the radii of the tWO follower faces 144 and 146, about 13.4 mm.

FIG. 10 shows schematically the position of the parts at the beginningof the film moving down-stroke. In this figure, as well as in FIGS. 7and 11, the shift cam 138 has moved the claw arm to the left in thedirection of projecting claw 122 into the film. In an actual design thethrow of cam 138 is about one thirty-second inch, throwing the followercenters 1145, 147 one sixty-fourth inch each side of the center linethrough the axis of shaft 134.

FIG. 11 shows schematically the positions of the parts at the end of thelm moving down-stroke. Cam rotation in the indicated direction betweenFIG. 10 and FIG. 11 is about 27. The angle subtended by the cam shiftruns 1-51 etc. at the shaft axis is about 35, but the claw arm has, inFIG. lil, swung about pin 124 about `8 in the direction opposite to thecam rotation. The film moving stroke thus occupies only about 27 of camand shaft rotation, safely leaving some 320 for shutter exposureopening. In the position of FIG. 11, shift cam 138 is still holding theclaw arm shifted to the left in the fi m.

FIG. 12 shows schematically the positions at the end of the dwell atstroke bottom, the position from which the return up-stroke then begins.In this position the cams have rotated 60 from the position of FIG. 11through the angle between radial lines a and b-and shift cam 1138 has-shifted the claw arm to the right to withdraw claw V122 from the film.The exposure opening of the shutter may commence during the movementbeween FIGS. 11 and 12.

FIG. 13 shows the positions on reaching the top of the upward returnstroke with shift cam 138 still holding the claw arm to the right. Thecam rotation from the position of FIG. 12 to FIG. 13 is the anglesubtended by shift runs 152, 162, about 35 plus the swing of the clawarm, making about 43 cam rotation.

From the position of FIG. 13 to that of FIG. 10 where the film movingdown-stroke starts the cam rotation is more than 210-the rotation of theradial line e in FIG. 13 Ito its position shown in FIG. 10. During thatrotation shift cam 138 shifts the claw arm to the left and the claw intothe film.

FIGS. 14, 15 and 16 show the single cam form of FIGS. 5 and 6 applied tothe claw arm. Here the single cam 90 is of the same form as in FIGS. 5and 6 and the same numerals are applied. The two cam followers 14011 and142a have the same follower surface radii, and are located on the clawarm 120, in the same relative positions, as in FIGS. 7 and followinr buthere they both engage the single cam 90, being offset from the same faceof 120 4to `overhang that cam. Cam 90 is attached to shaft 134 and adisk 90a also attached to the shaft may hold claw arm 120 against cam90. The film moving str-oke of the claw arm (down) occupies the samesmall cam rotation 4angle as in FIGS. 7 and following.

FIGS. `117 and 18 are diagrams illustrating the relative movements of acam and follower. In FIG. 17 a cam shift run A extends tangentially fromthe arc B of smaller radius to the point C where it meets the arc -D oflarger radius. The radius of curvature of the follower is here indicatedby the line E normal to A. That radius is here shown as the averagebetween the radii of B and D. Assume cam rotation relative to thefollower in the direction indicated, or relative follower rotation aboutthe cam axis in the opposite direction.

Upon the follower curvature reaching the point C on the cam, thefollower cen-ter then, relatively, swings in the arc E from the point Fto the point G where the follower radius is normal to A. From there onthe follower center moves, relatively, parallel to A to the point H. Thedescribed construction can be employed Ito analyze the cam action forany desired cam proportions and follower radius, the relations shownbeing illustrative.

The diagram of FIG. 18 shows the follower displacernent relative to thecam-concentric arc J plotted again-st relative cam advance in thedirection indicated; that relative displacement being, strictlyspeaking, the rectilinear displacement of a rectilinearly guided elementsuch as the registration element of FIGS. 1 and following. As will benoted from FIG. 18, the curve K of relative follower movement isessentially sinusoidal in character and is symmetric, or nearly so,about its center at L. `It follows that the two diametrically opposedfollowers constantly engage opposite sides of the cam device, whether aIsingle cam or a composite one. And it is apparent from FIG. 118 thatthe cam dri-ven follower movement is one of slow acceleration -anddeceleration. It has been found that the slight displacement of thefollowers relative to the cam, due to the swing of the claw arm,modifies their close cam engagement very slightly, so that even on theswinging claw arm there is no appreciable looseness between the camelement and the opposed followers. But it also h-as been found thatdecrease of the follower radii to` materially less than the larger camradius tends to introduce play during the cam stroke, while increase ofthe followerradii to much more than the larger cam radi-us introducesplay during the cam stroke. It will be understood that the opposed camfollowers, with their curvature centers diametrically opposed about thecam axis- .the axis of driving shaft 20 or 134-have their curved Aca-mengaging faces `diametrically opposed at a distance equal to the largercam radius plus the smaller cam radius. See, for instance, FIGS. 3 and7.

The form of claw arm drive shown, for example, in FIGS. 7 and followingmay Ibe used in combination with such a pilot pin drive as in FIG. t3.In other words, the claw arm drive of FIG. 1 may be that of FIG. 7. Therotational cam angle during which the pilot pin of FIG. 3 is in the iilmmay easily ybe increased to as much as 312 or more by reducing the camarcs between y84-84a and 86-86a to about 10. In FIG. 7, as shown, thecam rotational angle for the film movement is 27, leaving the iilmIstationary for 333. That -tilm shifting rotational angle-the rotationalangle of the shift runs 151 etc. and 161 etcmay be increased by 20 ormore by increasing the differences between what has been called thelarger and smaller cam radii, making the lm dwell equal to thecam-angular measure of pilot pin and film engagement.

It will be seen immediately from geometrical considerations that the camthrow equals -the difference lbetween the larger and smaller cam radii,and that the angle occupied by the cam stroke, commonly referred to asthe stroke angle, is the angle whose cosine is the ratio of the smallercam radius to the larger cam radius. That stroke angle is less by almost30% than the stroke angle of a conventional constant width cam,sometimes referred to as hea-rt shape, for the same ratio of larger tosmaller cam radii. Hence, for a given cam size and Ia given throw, thecam structure of the present invention permits the very substantialreduction in throw angle of substantially 30%.

The most satisfactory follower radius for any particular cam dimensionsand proportions may be determined in any desired manner, for example bycalculation, by direct test, or on the basis of experience. Calculationshows that, for a constant value of the larger cam rad-ius R1, theoptium value of the follower radius of curvature R3 is a nearly linearfunction of the smaller cam radius R2. If the criterion for selection ofthe follower radius is taken as accuracy of iit at the start and at theend of the cam stroke, calculation indicates that the follower rad-iusR3 should be close to the value given by the following equa- Insubstance, Equation 1 states that the follower radius exceeds the largercam radius by approximately `1/2 of the difference between the two camradii, that is, by approximately `1/2 of the cam throw. When thefollower radius is so chosen, the lit is typically within one or twothousandths of R1 during the initial and linal 10 or 15 of the camstroke, that is, during the entire stroke if the stroke angle does notexceed about 25. For larger stroke angles the cam may tend initially tobecome tight during the central portionof the cam stroke. Anyl bindingdue to that cause tends to disappear as the mechanism is broken in,presumably as the cam corners become very slightly rounded.

On the other hand, if the criterion is taken as the maintenance ofaccurate cam fit at the mid-point of the stroke, calculation indicatesthat the follower radius should be close to the value given by thefollowing equation:

The proportions dened by Equation 2 tend to perm-it slight play duringthe initial and iinal portions of the cam stroke, but maintain accurateiit at the mid-point. That is the point at which the mechanism that isdriven by the cam shifts from being accelerated to being decelerated.Accurate iit at that inflection point is particularly important foreliminating noise and vibration. In practice a follower radius exceedingthe larger cam radius by approximately 1A of the cam throw, insubstantial accordance with Equation 2, has been found to beparticularly satisfactory.

Particularly for cam stroke angles that are relatively small, as heredescribed, the preferred proportions are such that the follower radii ofcurvature are approximately the larger cam radius or, specifically, thatradius plus an amount that is equal to or somewhat less than '1/2 thedifference between the two cam radii, or plus an amount equal toapproximately 1A of that difference.

If the cam stroke angle is somewhat larger than described, it may beadvantageous to provide cam followers having convex curvature that isnot strictly circular, the radius of curvature having a value close tothat given by Equation 1, for example, near the axial plane of movement(the plane of FIG. 4) and becoming slightly smaller with increasingdistance from that plane. If it is preferred to maintain circularcurvature of the follower surfaces, the cam action can be improved forrelatively large cam throw by making the shift faces of the cam veryslightly convex, thereby reducing or eliminating the play that mayappear during the initial and iinal portions of the stroke when thefollower radius approximates that of Equation 2. However, a greatadvantage of the invention is that remarkably good tit is obtainablewith circular follower surfaces and with cams comprising only concentriccircular dwell surfaces and straight through surfaces. That isespecially true for cams of small throw angles providing the very rapidstroke that is an outstanding characteristic of the present invention,together with the slow acceleration and deceleration of the cam drivenelement illustrated diagramatically in FIGS. 17 and 18.

I claim:

1. In a kinetograph movement the combination of a cam driven elementguided for back and forth movement along a predetermined path,

a rotative cam means mounted for rotation about a fixed axis and havingtwo diametrically opposed peripheral circular arc portions of differentrad-ii centered on said axis and diametrically opposed substantiallystraight peripheral shift runs leading tangentially from the ends of thearc portion of smaller radius to the ends of the arc portion of largerradius,

a pair of cam followers mounted in normally fixed spaced relation on thecam driven element,

said followers having opposing substantially circular cam engaging facesconvexly curved toward the cam axis,

the centers of said convex follower curvatures lying in substantialdiametric opposition about the cam axis and their radii of curvaturesbeing substantially that of the radius of the circular arc portion oflarger radius of the cam means,

the relation between the smaller and larger cam radii and the curvatureradius of the convex follower faces being such as to closely oppositelyengage the cam means throughout its periphery and to give the cam drivenelement a shift movement of slowly increasing and decreasingacceleration and deceleration.

y 2. The combination defined in claim 1 and in which the convexcurvatures of said follower faces are circular and each of a radiusapproximately within the range between the larger cam radius and a valuethat exceeds the larger cam radius by about '1/2 of the differencebetween the two cam radii.

3. The combination defined in claim 2 and in which,

said cam means embodies two cam members axially spaced and rotatingtogether, each of said cam members being of the form specified in saidclaim,

and said cam followers being also axially spaced and each engaging asingle one of said cam members.

4. The combination defined in claim 1 and in which,

said cam means embodies two cam members axially spaced and rotatingtogether, each of said cam members being of the form specified in saidclaim,

and said cam followers being also axially spaced and each engaging asingle one of said cam members.

5. The combination defined in claim 4 and in which said cam drivenelement is a film register means guided for reciprocating movement alonga straight line.

6. The combination defined in claim 1 and in which the convex curvaturesof said follower faces are circular and each of a radius approximatelywithin the range between the larger cam radius and a value that exceedsthe larger cam radius by about `1/z of the difference between the twocam radii,

and in which said cam driven element is a lm register means guided forreciprocating movement along a straight line.

7. The combination defined in claim 6 and in which said film registermeans embodies a register carrying shaft guided for longitudinalreciprocation along a line of movement transverse of the -axis of camrotation,

and said cam followers being mounted on said shaft for normal movementtherewith.

8. The combination defined in claim 1 and in which the convex curvaturesof said follower faces are circular and each of a radius slightly largerthan the larger of the radii of the two circular arc portions of the cammeans said cam means embodies two cam members axially spaced androtating together, each of said cam members being of the form specifiedin said claim,

and in which said film engaging element is a film register meansembodying a register carrying shaft mounted for longitudinalreciprocation along a line of movement transverse of the rotational axisof the cam means,

the pair of cam followers being mounted on said shaft for normalmovement therewith,

and said cam followers being relatively displaced in a directionparallel to the rotational axis of the cam means commensurately with theaxial spacing of the cams, so that each cam operatively engages only oneof the followers.

9. The combination defined in claim 8 and in which,

the follower members each include a portion directly mounted on saidregister shaft for axial movement thereon,

and spring means acting on one of said portions and pressing saidportions into mutual abutment axially of the register shaft.

10. The combination defined in claim 9 and Ialso including a cammingmember mounted on the register shaft for rotation about the axis of thatshaft against a shaft abutment,

said spring means pressing the other of said follower portions axiallyagainst said camming member.

11. The combination defined in claim 1 and in which the cam drivenelement embodies a plate-like member carrying the pair of cam followersperipherally over hanging the cam means, and

the convex curvatures of said follower faces are substantially circularand each of a radius slightly larger than the larger of the radii of thetwocircular arc portions of the cam means.

12. The combination defined in claim 1 and in which the convexcurvatures of said follower faces are circular and each of a radiusapproximately within the range between the larger cam radius and a valuethat exceeds the larger cam radius by about 1/2 of the differencebetween the two cam radii,

said cam means embodies two cam members axially spaced and rotatingtogether, each of said cam members being of the form specified in saidclaim, and

said cam driven element embodying a plate-like member lying between said-spaced cam members and carrying the two cam followers off-set from itsopposite faces to each overhang one of the cam members.

13. In a kinetograph movement, the combination of a film engaging memberguided for movement back and forth along a predetermined line ofmovement and embodying a plate-like member,

a cam means rotatable about an axis normal to the plane of theplate-like member and embodying two cams axially spaced with saidplate-like member between them,

and a pair of cam followers integrated With and offset from oppositefaces of the plate-like member to each peripherally overhang one of saidcams.

14. In a kinetograph movement, the combination of a film engaging memberguided fo-r movement back and forth along a predetermined line ofmovement and embodying a plate-like member,

a cam means rotatable about an axis normal to the plane of theplate-like member and embodying a flat cam,

means holding the plate-like member atly against said cam,

and a pair of cam followers integrated with and offset from a face ofthe plate-like member to each peripherally overhang said cam,

each cam follower having a convex cam engaging face.

15. In a kinetograph movement, the combination of a film engagingelement mounted for back and forth movement along a predetermined path,

a cam means mounted for revolution about a fixed axis, said cam meanshaving two diametrically opposed peripheral circular arc portions ofdifferent radii centered on said axis and diametrically opposedsubstantially straight peripheral shift runs leading tangentially fromthe Iare portion of smaller radius to the ends of the arc portion oflarger radius,

a pair of cam followers mounted on the film engaging element in fixedspacing and having cam engaging faces in substantial diametricopposition about the cam axis,

said cam engaging faces being substantially circularly convexly curvedtoward the cam axis at substantially equal radii in the plane ofrotation of the cam means, the radius of convexity of said cam engagingfaces being of the order of the larger cam means radius.

16. In a kinetograph movement the combination of a cam driven elementguided for back and forth movement along a predetermined path,

a rotative cam means mounted for rotation about a fixed axis and havingtwo opposed peripheral and substantially circular arc portions ofdifferent radii centered on -said axis and substantially straightperipheral shift runs leading tangentially from the ends of the arcportion of smaller radius to the ends of the arc portion of largerradius,

a cam follower mounted on the cam driven element,

said follower having a substantially circular cam engaging face convexlycurved toward the cam axis and of a radius substantially that of theradius of the circular arc portion of larger radius of the cam means,the relation between the smaller and larger cam radii and the curvatureradius of the convex follower face being such -as to engage the cammeans throughout its periphery and to give the cam driven element ashift movement of slowly increasing and decreasing acceleration anddeceleration.

17. In a kinetograph movement the combination of a cam means mounted onand for rotation about the axis of a rotatable driving shaft,

a register carrying shaft mounted for longitudinal reciprocation along aline of movement transverse of the axis of said shaft,

a cam follower means mounted on said register shaft for longitudinalsliding movement thereon,

two abutment members mounted on -said register shaft and spacedlongitudinally from the opposite ends of the cam follower means,

a spring seated on one said abutment and pressing against the adjacentend of the follower means tending to move said follower meanslongitudinally away from said one abutment,

and a camming member mounted on the register shaft for rotation aboutthe axis of that shaft, said camming member bearing against the other ofsaid abutments and having camming action on the adjacent end of saidfollower means to move that means longitudinally against the action ofsaid spring when rotated about the axis of the register shaft,

said cam follower means comprising two substantially identical followermembers mounted. in longitudinal abutting relation on said registershaft and engaging opposite peripheral portions of the cam means.

References Cited by the Examiner UNITED STATES PATENTS 1,797,274 3/1931Ross 352-196 2,037,124 4/1936 Fear 226-57 2,816,457 12/ 1957 Sterzer74-569 M. HENSON WOOD, JR., Primary Examiner.

ROBERT B. REEVES, Examiner.

1. IN A KINETOGRAPH MOVEMENT THE COMBINATION OF A CAM DRIVEN ELEMENTGUIDED FOR BACK AND FORTH MOVEMENT ALONG A PREDETERMINED PATH, AROTATIVE CAM MEANS MOUNTED FOR ROTATION ABOUT A FIXED AXIS AND HAVINGTWO DIAMETRICALLY OPPOSED PERIPHERAL CIRCULAR ARC PORTIONS OF DIFFERENTRADII CENTERED ON SAID AXIS AND DIAMETRICALLY OPPOSED SUBSTANTIALLYSTRAIGHT PERIPHERAL SHIFT RUNS LEADING TANGENTIALLY FROM THE ENDS OF THEARC PORTION OF SMALLER RADIUS TO THE ENDS OF THE ARC PORTION OF LARGERRADIUS, A PAIR OF CAM FOLLOWERS MOUNTED IN NORMALLY FIXED SPACEDRELATION ON THE CAM DRIVEN ELEMENT, SAID FOLLOWERS HAVING OPPOSINGSUBSTANTIALLY CIRCULAR CAM ENGAGING FACES CONVEXELY CURVED TOWARD THECAM AXIS, THE CENTERS OF SAID CONVEX FOLLOWER CURVATURES LYING INSUBSTANTIAL DIAMETRIC OPPOSITION ABOUT THE CAM AXIS